The invention relates to an apparatus at a spinning preparation machine, especially a flat card, roller card or the like, for ascertaining carding process variables, wherein a clothed, rapidly rotating roller is located opposite at least one clothed component.
It is known to associate with the clothed component, in contact therewith, a piezoelectric sensor which is connected to an electrical evaluation device in communication with a display device and/or switching device. More particularly, from EP 1 215 312 A1 it is known, in the case of a revolving card top and a stationary carding segment, to measure the carding forces (shear forces) at both carding elements using a piezoelectric layer in each case. These piezoelectric layers are connected to a measurement apparatus. The measurement apparatus passes a corresponding signal to a control and regulation device. The carding forces are measured by means of piezoelectric layers and the associated measurement apparatuses and are passed to the control and regulation device by means of signals. In that arrangement, the carding force at the fixed carding element or at the revolving card top is determined by means of force measurement. It is disadvantageous that the carding forces, which are caused by the fibres between the tips, are minimal and the carding force sensors have a high weight owing to their freely movable carding elements. A further disadvantage lies in the fact that the mass inertia of such a system is very high. Accordingly, the resultant difference between the baseline signal and the useful signal is vanishingly small. If the weight of such a sensor is reduced, the rigidity of the system is reduced and sagging of the carding element is increased, whilst the measurement result is falsified because the spacing between the sensor and the roller changes. In the case of the known apparatus, the force sensor cuts through the lines of force, so that forces and shear forces can be detected. In the process, it is immaterial whether the piezo sensor detects the shear forces between the clothing and carding component holder or, for example, with respect to the side screen, because the lines of force pass through the entire structural unit. Because a force sensor cuts through lines of force, it must always rest against a component. For example, the clothing rests against the carding component, or the carding component rests against the side screen (corresponding force sensors between those components). Therefore it is not possible, in operation, to move a force sensor from one component to another component without changing settings, that is to say without undoing and re-fixing components, and interrupting lines of force. A constant force at the clothing produces a constant force at the piezo sensor and therefore a carding force produces no change in the piezo signal. Electrical filtering of the signal is not necessary because the forces from other machine regions do not influence the carding force measurement. Finally, the outlay for the measurement is, in terms of apparatus, high because the carding component has to be modified for the purpose of integrating the sensor.
The problem underlying the invention is accordingly to provide an apparatus of the kind described at the beginning that avoids the mentioned disadvantages and that especially makes it possible, by means that are simple in terms of construction, to ascertain the intensity of contact between fibres and the fibre-guiding clothing of the component (the carding intensity).
As a result of the fact that the piezoceramic sensor is a structure-borne sound sensor of high sensitivity, which is associated with a component and in contact therewith, it is possible to ascertain the carding intensity by means that are simple in terms of construction. The structure-borne sound sensor is merely coupled up to a component in which structure-borne sound vibrations occur, as a result of which those structure-borne sound vibrations also pass into and flow through the structure-borne sound sensor, and the vibrations can be detected by means of a measurement arrangement. If the structure-borne sound sensor and the fixed carding element are so constructed that, for example, their connection is, advantageously, magnetic in nature, the structure-borne sound sensor can, in the course of continuing production, be moved from carding element to carding element, being placed thereon, and the carding intensity can be measured. It is accordingly possible, within the shortest time, to investigate all the carding locations of a flat card, including the card top, with regard to the carding intensity thereof, in the course of continuing production. As a result of the fact that the structure-borne sound sensor, which is, for example, a small cuboid, is fixed in, for example, an existing fixed carding element or revolving card top, functions of the fixed carding element or revolving card top are in no way curtailed by a change in geometry etc.
In the course of carding, the fibres produce a transverse vibration in the clothing, which propagates through the entire carding component. If the piezo sensor is attached to a carding component through which vibrations pass, the vibration also runs through this mounted sensor. Consequently, the vibration also causes deformation of that component, that is to say the vibration can be described by means of the piezo sensor. Even in the case of a constant force at the clothing, a change in the piezo signal occurs. Electrical filtering of the signal is necessary because the vibrations from other machine regions influence the structure-borne sound measurement. Low-frequency vibrations of all moving components are filtered out. The apparatus is simple in terms of construction, as the piezo sensor merely has to be placed on the component.
The structure-borne sound sensor is advantageously of high sensitivity. Preferably, the sensitivity of the structure-borne sound sensor is about 10 V/N to 50 V/N, especially about 25 V/N to 35 V/N. The structure-borne sound sensor may be capable of detecting vibrations in the range from about 2.5 kHz to 12.5 kHz. In certain preferred embodiments, the evaluation device is capable of filtering out low-frequency vibrations, for example, is capable of filtering out frequencies outside the range of about 2.5 kHz to 12 kHz. One illustrative evaluation device has a frequency analysis function (Fourier analysis). A high-pass filter may be used. In certain preferred arrangements, carding is carried out between a clothing-carrying roller and a carding element, a piezoceramic structure-borne sound sensor being associated with one of the clothing-carrying components. The structure-borne sound sensor may, for example, be arranged directly on the rear side of the clothing. The structure-borne sound sensor may, for example, be fixed in the middle of the machine width. In some embodiments, the structure-borne sound sensor is fixed in a fixed carding segment. In other embodiments, the structure-borne sound sensor is fixed in a revolving card top. The structure-borne sound sensor may be fixed to the component by means of adhesion. Other suitable fixing methods include fixing by means of magnetic force, by means of a screw connection, or by means of a shape-based connection. In some embodiments, the structure-borne sound sensor is externally fixed on a component carrying a clothing strip. There may in some arrangements be a direct structure-borne sound line between clothing support and adapter plate, for example, by means of a screw connection. In certain embodiments, the structure-borne sound sensor is fixed on a plate which is flexibly associated with different clothing-strip-carrying components by means of a rapid closure. The rapid closure may be provided, for example, by means of a shape-based or force-based connection. It is advantageous for the structure-borne sound sensor signals to be so filtered that the signal contains no components of structure-borne sound vibrations of the spinning preparation machine that are caused by moving parts of the machine. For example, all structure-borne sound vibrations less than 2.5 kHz are filtered out from the structure-borne sound sensor signals. It is preferred that there are used solely those components of the structure-borne sound sensor signal that are caused by the fibre movement between the carding parts of the machine. The structure-borne sound sensor signals may be evaluated, for example, by means of statistical evaluation methods (mean, standard deviation, CV value). The structure-borne sound sensor signals may, for example, be integrated. The structure-borne sound sensor signals in their course over time and in the frequency range may, for example, be evaluated by means of statistical evaluation methods. The structure-borne sound sensor signals may, for example, be logarithmised to avoid over-valuation of signal peaks. In one embodiment, in the frequency range the structure-borne sound sensor signal curves “with fibre material” are deduced from those “without fibre material” and the course of the difference in the frequency range is evaluated.
The carding intensity “with fibre material” may be subtracted from “without fibre material”. Instead, the carding intensity “with fibre material” may be divided by “without fibre material”. Signal peaks in the course over time may be evaluated as thick places. The variables standard deviation and CV value represent a measure of the fibre unraveling. From the determined data, carding intensity classes (amplitude; frequency) are formed in order to be able to evaluate the pulses in detail. With fixed carding between two carding components there will be clearly associated at least one carding coefficient which reflects the carding intensity. On the basis of the carding intensity information at each carding component, the clothing wear can, for example, be assessed and the setting checked. The carding intensity of the machine as a whole can be determined by accumulation of individual measurements and can be set against a quality statement for the machine, for example, flat card. Illustrative of a quality statement for a flat card would be: 95 neps/g; 9.8% short fibres.
In certain embodiments there may be a multiplicity of carding elements and each carding element may have its own structure-borne sound sensor associated with it. In other embodiments, the structure-borne sound sensor is in the form of a portable unit which can be used on any machine. In yet further embodiments, the apparatus is so arranged that the operator can associate one and the same structure-borne sound sensor with each carding element in succession, in accordance with a fixed program sequence. The structure-borne sound sensor signals of more than two carding elements may be evaluated relative to one another. In some embodiments, the grading of the carding elements for example with respect to the number of ties, spacing, clothing condition, clothing type, can be assessed by means of the structure-borne sound sensor signal, by comparing the carding coefficients of all the carding elements with specifications relating to desirable grading of the carding intensity. Preferably, in the comparison of the carding coefficients of different carding elements the carding coefficients are normalisable. If desired, the structure-borne sound sensor can be used for analysis at fibre-guiding components, for example web guide, pressure bar, holding-down device, webspeed, funnel, cover plates at the transfers from rollers (drum-doffer).
In certain preferred arrangements, the machine is a flat card and the structure-borne sound sensor is associated with the revolving card top, is fixed in or on it and revolves with it. The structure-borne sound sensor may be fixed in a stationary position on the track of the revolving card top flats. Instead, there may be attached to the structure-borne sound sensor a structure-borne sound guide plate, for example, a spring steel plate, by means of which the structure-borne sound of the revolving card top flats is detected and conveyed to the structure-borne sound sensor. The structure-borne sound sensor may in some embodiments be directly or indirectly associated with a blade in order to quantify the waste separation, that is to say composition and amount. It is preferred that the apparatus includes a control system, the clothing condition, that is to say new or worn clothing, for example of a clothing strip, being determined using the structure-borne sound sensor, by means of the fact that the carding coefficient is determined and monitored by the control system and a warning being issued by the control system in the event of a limit value being exceeded. A portable structure-borne sound sensor unit with evaluation device may, in preferred embodiments, consist of, for example, a display for output of the carding coefficient, a start button for activation of the measurement and an LED for display of the operating situation.
In the case of revolving card flats, in one embodiment a first flat, having a clothing, carries the structure-borne sound sensor and a second flat, not having a clothing, having on-board electronics units, runs behind the first flat. The first flat is advantageously connected to the second flat by a sensor cable. Between the first flat (having a clothing) and the second flat (having electronics units) there may be arranged no flat or at least one flat having a clothing. The sensor may be associated with a holding element, for example, a clasp or the like, in contact with and touching at least two different wall surfaces of the carrier member. The clasp may be associated with the card flat by means of a shape-based or force-based connection. The clasp may be so associated with the card flat that the sensor is arranged inside the card flat or outside the card flat. The signals of the structure-borne sound sensor are advantageously recordable throughout its travel over the flexible bend. Instead, the signals of the structure-borne sound sensor can be recorded at particular places over the flexible bend, over a period of time. The signals can advantageously be recorded at each change of setting of the card flat. In preferred embodiments, a plurality of structure-borne sound sensors are attached by clasps to a card flat, preferably on both sides, that is, on the left and right sides of the machine. In one embodiment, a clasp and sensor are associated with a carding flat, and an electronics unit can also be arranged, for example, can be insertable, in the same flat in the form of an insert variant.
The invention also provides an apparatus at a spinning preparation machine, especially a flat card, roller card or the like, wherein a clothed, rapidly rotating roller is located opposite at least one clothed component, there being associated with the component, in contact therewith, a piezoelectric sensor which is connected to an electrical evaluation device in communication with a display device and/or switching device, wherein the piezoelectric sensor is a structure-borne sound sensor of high sensitivity and the electrical evaluation device is capable of determining from the structure-borne sound the intensity of contact between fibres and the fibre-guiding clothing of the component (the carding intensity).